Drinking expired sparkling water is almost certainly not going to make you sick. The date printed on the bottle is a quality indicator, not a safety deadline. The FDA considers properly produced, unopened bottled water to have an unlimited shelf life, and manufacturers add dates primarily because of concerns about taste and odor changes over time. That said, “expired” sparkling water won’t taste the same as fresh, and in some cases the packaging itself becomes the real issue.
Why the Expiration Date Exists
Bottled water companies stamp dates on their products voluntarily. The FDA does not require expiration dates on bottled water because, sealed and stored correctly, the water itself doesn’t spoil. What changes is the drinking experience. Carbonated water gradually loses its fizz, and the plastic bottle can subtly alter the flavor over months of storage. The date is the manufacturer’s estimate of when those changes become noticeable enough to disappoint you.
What Actually Changes After the Date
The most obvious change is carbonation loss. Carbon dioxide slowly escapes through packaging over time, and the rate depends heavily on the container. Glass bottles lose very little, leaking roughly 0.12 to 0.68 mL of CO2 per day. PET plastic bottles, the most common type on store shelves, can lose up to 60% of their carbonation over time. Aluminum cans fall somewhere in between. So if your sparkling water has been sitting in a plastic bottle for months past its date, expect it to taste flat or nearly flat.
Flavor can also shift. Plain sparkling water may develop a slightly stale or “off” taste from prolonged contact with plastic. Flavored varieties that contain citric acid or other additives may taste different as those compounds interact with the packaging material over extended storage.
The Plastic Bottle Problem
The bigger concern with long-expired sparkling water isn’t the water itself. It’s what the bottle releases into it. PET plastic bottles can leach small amounts of chemicals over time, and two factors accelerate this: heat and sunlight.
Antimony, a compound used in manufacturing PET plastic, migrates into the liquid more readily when bottles sit in sunlight for extended periods. Research on carbonated beverages stored in PET bottles found that antimony concentrations were consistently higher in sunlight-exposed samples compared to those kept at room temperature, and the levels increased the longer the bottles sat. Warm temperatures also promote the release of plastic-derived chemicals into the water, though sunlight appears to have a stronger effect than heat alone.
Phthalates, another class of chemicals associated with plastic packaging, also migrate into bottled liquids over time. Studies on acidic liquids stored in PET and HDPE bottles found measurable phthalate levels after months of storage, with higher concentrations at elevated temperatures. Even so, the highest levels detected in research remained well below the EPA’s maximum allowable contaminant level for drinking water (6 µg/L). The amounts are tiny, but they increase with time and poor storage conditions.
The practical takeaway: a bottle of sparkling water a few months past its date, stored in a cool pantry, poses minimal chemical concern. A bottle that’s been sitting in a hot garage or a sunny car for months is a different story.
Bacterial Growth Is Unlikely in Sealed Bottles
Unopened, commercially sealed sparkling water is not a hospitable environment for bacteria. The carbonation creates an acidic environment (carbonic acid), and the sealed container prevents contamination. The risk of bacterial growth applies mainly to bottles that have been opened, improperly sealed, or stored in warm conditions for long periods. If your sealed bottle looks normal, with no cloudiness, discoloration, or bulging, bacteria are not a realistic concern.
Once opened, any bottled water becomes vulnerable. Warm temperatures foster bacterial growth quickly, and an opened bottle left out can develop enough bacteria to cause nausea, stomach pain, or diarrhea. But that’s true of any water, expired or not.
Flavored and Diet Sparkling Water
If your expired sparkling water contains artificial sweeteners, there’s a slightly different consideration. Aspartame, one of the most common sweeteners in diet beverages, breaks down over time. Light exposure dramatically speeds this process, with research showing that simulated sunlight caused aspartame in soft drinks to degrade up to ten times faster than in controlled conditions. This degradation produces transformation products, some of which preliminary toxicity modeling suggests could be more harmful than aspartame itself.
This research is still in early stages, and the practical risk from drinking one old bottle of diet sparkling water is not well established. But if you have flavored or diet sparkling water that’s significantly past its date and has been stored in a sunny spot, the taste will likely be off, and there’s less reason to push through and drink it.
How to Tell If It’s Still Worth Drinking
Check the packaging first. If a plastic bottle looks warped, yellowed, or feels unusually soft, toss it. These are signs of heat damage or UV degradation that increase the likelihood of chemical leaching. For cans, look for dents, rust, or bulging.
If the packaging looks fine, open it and assess. A sealed bottle that still hisses when you crack it open has retained at least some carbonation. Taste a small sip. Flat, stale, or plasticky flavors are your cue to pour it out. None of these off flavors indicate something dangerous, but they do mean the water is past its prime.
Plain sparkling water in glass bottles holds up the longest. PET plastic bottles stored in cool, dark conditions are next best. Anything stored in heat or direct sunlight degrades fastest, regardless of container type.